Re: How to declare a bind mount in the "file-systems" definition?

[Matthew Brooks <matthewfbrooks@mailbox.org>]

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Thanks for the help! I've renamed the section and hard wrapped the lines, and updated it to a more recent commit.

Let me know if there's anything else I should do.


On Wed, 8 Apr 2020 12:52:47 -0400
Leo Famulari <leo@famulari.name> wrote:

> On Sun, Mar 29, 2020 at 03:01:09PM -0500, Matthew Brooks wrote:
> > I can give it a shot. I've whipped up and attached a quick patch that adds a section about bind-mounting.
> > I wasn't able to find any info on how to preview the resulting html file though, or on what the preferred writing style is for the cookbook.  
> 
> Thanks!
> 
> You can build the cookbook as HTML like this:
> 
> `guix environment --pure guix -- make doc/guix-cookbook.html`
> 
> When building you will see some errors and warnings that need to be
> fixed, related to setting up the menu and navigating between sections.
> 
> Lines should be wrapped at 72 characters, except in examples.
> 
> >  * Customizing the Kernel::     Creating and using a custom Linux kernel on Guix System.
> > +* Bind-mounting file systems:: Setting up a bind-mount in the file-systems definition.  
> 
> "Setting up a bind-mount on Guix System" is more general, and thus I
> think more appropriate for the table of contents.
> 
> Otherwise LGTM! Can you send a revised patch?


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diff --git a/doc/guix-cookbook.texi b/doc/guix-cookbook.texi
index 58a5ba1c80..b4522c0637 100644
--- a/doc/guix-cookbook.texi
+++ b/doc/guix-cookbook.texi
@@ -1322,6 +1322,7 @@ reference.
 @menu
 * Customizing the Kernel::       Creating and using a custom Linux kernel on Guix System.
 * Customizing a Window Manager:: Handle customization of a Window manager on Guix System.
+* Setting up a bind-mount on Guix System:: Setting up a bind-mount in the file-systems definition.
 @end menu
 
 @node Customizing the Kernel
@@ -1614,6 +1615,55 @@ Then you need to add the following code to a StumpWM configuration file
 (set-font (make-instance 'xft:font :family "DejaVu Sans Mono" :subfamily "Book" :size 11))
 @end lisp
 
+@node Setting up a bind-mount on Guix System
+@section Setting up a bind-mount on Guix System
+
+To bind-mount a file-system, one must first set up some definitions
+before the @code{operating-system} section of the system definition. In
+this example we will bind-mount a folder from a spinning disk drive to
+@code{/tmp}, to save wear and tear on the primary SSD, without
+dedicating an entire partition to be mounted as @code{/tmp}.
+
+First, the source drive that hosts the folder we wish to bind mount
+should be defined, so that the bind-mount can depend on it.
+
+@lisp
+(define source-drive ;; "source-drive" can be named anything you want.
+   (file-system
+    (device (uuid "UUID goes here"))
+    (mount-point "/path-to-spinning-disk-goes-here")
+    (type "ext4"))) ;; Make sure to set this to the appropriate type for your drive.
+@end lisp
+
+The source folder must also be defined, so that guix will know it's not
+a regular block device, but a folder.
+@lisp
+(define (%source-directory) "/path-to-spinning-disk-goes-here/tmp") ;; "source-directory" can be named any valid variable name.
+@end lisp
+
+Finally, inside the @code{file-systems} definition, we must add the
+mount itself.
+
+@lisp
+(file-systems (cons*
+
+                ...<other drives omitted for clarity>...
+
+                source-drive ;; Must match the name you gave the source drive in the earlier definition.
+
+                (file-system
+                 (device (%source-directory)) ;; Make sure "source-directory" matches your earlier definition.
+                 (mount-point "/tmp")
+                 (type "none") ;; We are mounting a folder, not a partition, so this type needs to be "none"
+                 (flags '(bind-mount))
+                 (dependencies (list source-drive)) ;; Ensure "source-drive" matches what you've named the variable for the drive.
+                 )
+
+                 ...<other drives omitted for clarity>...
+
+                ))
+@end lisp
+
 @c *********************************************************************
 @node Advanced package management
 @chapter Advanced package management